CHAPTER XI

HUMBLE-BEES AND OTHER MATTERS.

Two humble-bees, Bombus thoracicus and B. violaceus, are found on the pampas; the first, with a primrose yellow thorax, and the extremity of the abdomen bright rufous, slightly resembles the English B. terrestris; the rarer species, which is a trifle smaller than the first, is of a uniform intense black, the body having the appearance of velvet, the wings being of a deep violaceous blue.

A census of the humble-bees in any garden or field always shows that the yellow bees outnumber the black in the proportion of about seven to one; and I have also found their nests for many years in the same proportion; about seven nests of the yellow to one nest of the black species. In habits they are almost identical, and when two species so closely allied are found inhabiting the same locality, it is only reasonable to infer that one possesses some advantage over the other, and that the least favoured species will eventually disappear. In this case, where one so greatly outnumbers the other, it might be thought that the rarer species is dying out, or that, on the contrary, it is a new-comer destined to supplant the older more numerous species. Yet, during the twenty years I have observed them, there has occurred no change in their relative positions; though both have greatly increased in numbers during that time, owing to the spread of cultivation. And yet it would scarcely be too much to expect some marked change in a period so long as that, even through the slow-working agency of natural selection; for it is not as if there had been an exact balance of power between them. In the same period of time I have seen several species, once common, almost or quite disappear, while others, very low down as to numbers, have been exalted to the first rank. In insect life especially, these changes have been numerous, rapid, and widespread.

In the district where, as a boy, I chased and caught tinamous, and also chased ostriches, but failed to catch them, the continued presence of our two humble-bees, sucking the same flowers and making their nests in the same situations, has remained a puzzle to my mind.

The site of the nest is usually a slight depression in the soil in the shelter of a cardoon bush. The bees deepen the hollow by burrowing in the earth; and when the spring foliage sheltering it withers up, they construct a dome-shaped covering of small sticks, thorns, and leaves bitten into extremely minute pieces. They sometimes take possession of a small hole or cavity in the ground, and save themselves the labour of excavation.

Their architecture closely resembles that of B. terrestris. They make rudely-shaped oval honey-cells, varying from half an inch to an inch and a half in length, the smaller ones being the first made; later in the season the old cocoons are utilized for storing honey. The wax is chocolate-coloured, and almost the only difference I can find in the economy of the two species is that the black bee uses a large quantity of wax in plastering the interior of its nest. The egg-cell of the yellow bee always contains from twelve to sixteen eggs; that of the black bee from ten to fourteen; and the eggs of this species are the largest though the bee is smallest. At the entrance on the edge of the mound one bee is usually stationed, and, when approached, it hums a shrill challenge, and throws itself into a menacing attitude. The sting is exceedingly painful.

One summer I was so fortunate as to discover two nests of the two kinds within twelve yards of each other, and I resolved to watch them very carefully, in order to see whether the two species ever came into collision, as sometimes happens with ants of different species living close together. Several times I saw a yellow bee leave its own nest and hover round or settle on the neighbouring one, upon which the sentinel black bee would attack and drive it off. One day, while watching, I was delighted to see a yellow bee actually enter its neighbour's nest, the sentinel being off duty. In about five minutes' time it came out again and flew away unmolested. I concluded from this that humble-bees, like their relations of the hive, occasionally plunder each other's sweets. On another occasion I found a black bee dead at the entrance of the yellow bees' nest; doubtless this individual had been caught in the act of stealing honey, and, after it had been stung to death, it had been dragged out and left there as a warning to others with like felonious intentions.

There is one striking difference between the two species. The yellow bee is inodorous; the black bee, when angry and attacking, emits an exceedingly powerful odour: curiously enough, this smell is identical in character with that made when angry by all the wasps of the South American genus Pepris--dark blue wasps with red wings. This odour at first produces a stinging sensation on the nerve of smell, but when inhaled in large measure becomes very nauseating. On one occasion, while I was opening a nest, several of the bees buzzing round my head and thrusting their stings through the veil I wore for protection, gave out so pungent a smell that I found it unendurable, and was compelled to retreat.

It seems strange that a species armed with a venomous sting and possessing the fierce courage of the humble-bee should also have this repulsive odour for a protection. It is, in fact, as incongruous as it would be were our soldiers provided with guns and swords first, and after with phials of assafoatida to be uncorked in the face of an enemy.

Why, or how, animals came to be possessed of the power of emitting pestiferous odours is a mystery; we only see that natural selection has, in some mstances, chiefly among insects, taken advantage of it to furnish some of the weaker, more unprotected species with a means of escape from their enemies. The most stinking example I know is that of a large hairy caterpillar I have found on dry wood in Patagonia, and which, when touched, emits an intensely nauseous effluvium. Happily it is very volatile, but while it lasts it is even more detestable than that of the skunk.

The skunk itself offers perhaps the one instance amongst the higher vertebrates of an animal in which all the original instincts of self-preservation have died out, giving place to this lower kind of protection. All the other members of the family it belongs to are cunning, swift of foot, and, when overtaken, fierce-tempered and well able to defend themselves with their powerful well-armed jaws.

For some occult reason they are provided with a gland charged with a malodorous secretion; and out of this mysterious liquor Nature has elaborated the skunk's inglorious weapon. The skunk alone when attacked makes no attempt to escape or to defend itself by biting; but, thrown by its agitation into a violent convulsion, involuntarily discharges its foetid liquor into the face of an opponent. When this animal had once ceased to use so good a weapon as its teeth in defending itself, degenerating at the same time into a slow-moving creature, without fear and without cunning, the strength and vileness of its odour would be continually increased by the cumulative process of natural selection: and how effective the protection has become is shown by the abundance of the species throughout the whole American continent. It is lucky for mankind--especially for naturalists and sportsmen--that other species have not been improved in the same direction.

But what can we say of the common deer of the pampas (Cervus campestris), the male of which gives out an effluvium quite as far-reaching although not so abominable in character as that of the Mephitis? It comes in disagreeable whiffs to the human nostril when the perfumer of the wilderness is not even in sight. Yet it is not a protection; on the contrary, it is the reverse, and, like the dazzling white plumage so attractive to birds of prey, a direct disadvantage, informing all enemies for leagues around of its whereabouts. It is not, therefore, strange that wherever pumas are found, deer are never very abundant; the only wonder is that, like the ancient horse of America, they have not become extinct.

The gauchos of the pampas, however, give _a reason_ for the powerful smell of the male deer; and, after some hesitation, I have determined to set it down here, for the reader to accept or reject, as he thinks proper. I neither believe nor disbelieve it; for although I do not put great faith in gaucho natural history, my own observations have not infrequently confirmed statements of theirs, which a sceptical person would have regarded as wild indeed. To give one instance: I heard a gaucho relate that while out riding he had been pursued for a considerable distance by a large spider; his hearers laughed at him for a romancer; but as I myself had been attacked and pursued, both when on foot and on horseback, by a large wolf-spider, common on the pampas, I did not join in the laugh. They say that the effluvium of C. campestris is abhorrent to snakes of all kinds, just as pyrethrum powder is to most insects, and even go so far as to describe its effect as fatal to them; according to this, the smell is therefore a protection to the deer. In places where venomous snakes are extremely abundant, as in the Sierra district on the southern pampas of Buenos Ayres, the gaucho frequently ties a strip of the male deer's skin, which retains its powerful odour for an indefinite time, round the neck of a valuable horse as a protection. It is certain that domestic animals are frequently lost here through snake-bites. The most common poisonous species--the Craspedo-cephalus alternatus, called _Vivora de la Cruz_ in the vernacular--has neither bright colour nor warning rattle to keep off heavy hoofs, and is moreover of so sluggish a temperament that it will allow itself to be trodden on before stirring, with the result that its fangs are not infrequently struck into the nose or foot of browsing beast. Considering, then, the conditions in which C. campestris is placed--and it might also be supposed that venomous snakes have in past times been much more numerous than they are now--it is not impossible to believe that the powerful smell it emits has been made protective, especially when we see in other species how repulsive odours have been turned to account by the principle of natural selection.

After all, perhaps the wild naturalist of the pampas knows what he is about when he ties a strip of deer-skin to the neck of his steed and turns him loose to graze among the snakes.

The gaucho also affirms that the deer cherishes a wonderful animosity against snakes; that it becomes greatly excited when it sees one, and proceeds at once to destroy it; _they say,_ by running round and round it in a circle, emitting its violent smell in larger measure, until the snake dies of suffocation. It is hard to believe that the effect can be so great; but that the deer is a snake hater and killer is certainly true: in North America, Ceylon, and other districts deer have been observed excitedly leaping on serpents, and killing them with their sharp cutting hoofs.

##